Police in Vietnam have detained a former chairperson and general director of the private Ocean Bank as part of an investigation into alleged lending fraud of one of the country's richest men.

Nguyen Minh Thu was arrested on Monday (Jan. 26), and will be in police custody for four months on suspicion of “seriously violating state regulations on economic management,” police said Wednesday.

Ironically, Thu was appointed in October 2014 by the Ocean Bank’s board as its chairperson to replace business tycoon Ha Van Tham, who was arrested by the police in response to a central bank investigation that found "serious violations" in lending.

Thu had been the bank’s general director since 2011.

The bank’s board last month appointed Dao Thi Thuy as its new chairperson.

The bank’s parent company, Ocean Group, which has interests in real estate, banking, securities, retail, media and hotels, has lost half of its value since the arrest of the US-educated Tham.

Nguyen Van Hoan, a deputy general director of Ocean Bank, is also in police custody for the investigation.